The present invention generally relates to magnetic recording and reproducing systems, and more particularly to a magnetic recording and reproducing system for recording and reproducing a video signal and a digital audio signal on and from a magnetic tape.
Conventionally, there are systems for recording and reproducing a frequency modulated (FM) audio signal on and from a deep layer portion of a magnetic layer on a magnetic tape by use of rotary audio heads and recording and reproducing a video signal on and from a surface layer portion of the magnetic layer on the magnetic tape by use of rotary video heads. According to such systems, since the FM audio signal is an analog signal, the quality of the audio signal becomes deteriorated every time a dub-recording is carried out on the FM audio signal.
For these reasons, in the so-called 8-mm video tape recorders or cameras, a digital audio signal is recorded in a portion of a track which is recorded by the rotary video head. The deterioration in the quality of the audio signal introduced by the dub-recording is extremely small because the audio signal is recorded and reproduced in the form of a digital signal.
In the 8-mm video tape recorder, the analog audio signal is digitized for every one field of the video signal. However, the field frequency depends on the television system. In other words, the field frequency is 60 Hz in the case of a monochrome video signal of M-system, the field frequency is 59.94 Hz in the case of the NTSC system color video signal, and the field frequency is 50 Hz in the case of the PAL system color video signal or the like.
For this reason, there is a problem in that synchronism of the video signal and the digital audio signal cannot be obtained between a first apparatus for recording and reproducing the video signal having the field frequency of 50 Hz and a second apparatus for recording and reproducing the video signal having the field frequency of 59.94 Hz or 60 Hz. In order to obtain synchronism of the video signal and the digital audio signal, the sampling frequency of the analog audio signal must be changed between the first and second apparatuses, or the encoding algorithm must be greatly modified between the first and second apparatuses.